FAQ: Fuel System & Fuel System Components

Fuel System FAQ

Below are the answers to some of our most commonly asked questions about fuel systems & the components. Whether it's a question about the fuel harnesses or which pumps fit in the divisionX fuel hats, you can find your answer below. If your question isn't answered below, give us a shout by email (support@lethalperformance.com) or call us at 561-753-8105 and speak with one of our reps.

By Lethal Performance

The Fuel System Wiring Harness


Dual Pump Return Style Fuel System Harness

The Lethal Performance Dual Harness is meant to run two fuel pumps in a return style configuration. The wire harness consists of a fusible link, wire, 2 relays, fuses and a 6 pin connector at the end of it. The fusible link is the pair of short gray wires with the ring terminal at the end of it. This is to be installed on the positive battery terminal at the fuse box. The red power wire from the harness gets crimped and heat shrinked onto the fusible link.

Relay wires on the harness:

Large Gauge Red / Yellow Wires - Positive Power Wires

Large Gauge Black Wires - Ground Wires

Blue Wires - Trigger Wires (Used to trigger the relays when battery power is keyed on. You will need to tap into your factory FPDM wire to trigger the relays. See chart below.)

 

The small Black wires with the ring terminal on them are your ground. You will ground the ring terminal to a good ground on the chassis. If there is paint or any type of coating on the place where you intend to ground the relays you will need to use some sandpaper to remove the paint/coating in order to get a proper ground Fuses

Each relay has a blade fuse between the relay itself and the pump. If there is a short at the pump the fuse will pop protecting the relay and anything in line before the relay from shorting out.

The 6-Pin Connector and Wire Colors

The 6-pin connector at the end of the dual relay harness was designed to work as a plug and play solution for the DX-SN016 fuel hat which uses the same style connector on the hat.

If you have a 99-04 GT/Mach-1/Cobra then all you will need to do is plug the 6-pin connector at the end of the harness into the connector on the fuel hat. There will be 2 remaining wires on the harness with butt connectors on them. These are the small yellow and small black wires. These wires are for the fuel level sender. You will need to peel back the wire loom from your factory harness where it used to connect to the factory fuel hat assembly. You will have 2 larger gauge wires which are for fuel pump power and ground. There will also be 2 smaller gauge wires which are for the level sender. We typically connect the yellow wire on the Lethal harness to the small colored wire on the factory harness and the black wire to the dark color. The color of your factory level sender wires may vary but they will always be the smaller wires on the factory harness.

For 2005+ Mustangs using the dual harness you will cut the 6-pin connector off of the end of the Lethal harness to make the connection to the aftermarket fuel hat. The wire colors on most aftermarket fuel hats for power and ground are red (+) and black (-). Once you've cut the 6-pin connector off of our harness you'll then connect the yellow and orange wires on our harness to the red wires on the fuel hat for power and the black wires on the Lethal harness to the black wires on the fuel hat for ground. You'll be left with 2 remaining wires on the fuel hat which are for the level sender. You will need to peel back the wire loom from your factory harness where it used to connect to the factory fuel hat assembly. Depending on the model/year you will see several larger gauge wires which are for the fuel pump power and ground. There will also be 2 smaller gauge wires which are for the level sender. We typically connect the yellow wire on the Lethal harness to the small colored wire on the factory harness and the black wire to the dark color. However on 2005+ cars it's not imperative to match colors for the levels senders as the sending units run off of resistance not power and ground. So you can connect the level sender wires any way you like and they will allow the sending unit to function properly.

Triple Pump Return Style Fuel System Harness

The Lethal Performance Triple Relay Harness is meant to run two or three fuel pumps in a return style configuration. The wire harness consists of a fusible link, wire, 3 relays, fuses and a 6 pin connector at the end of it. The fusible link is the 3 short gray wires with the ring terminal at the end of it. This is to be installed on the positive battery terminal at the fuse box. The red power wire from the harness gets crimped and heat shrinked onto the fusible link.

Relay wires on the harness:

Large Gauge Red / Yellow Wires - Positive Power Wires

Large Gauge Black Wires - Ground Wires

Blue Wires - Trigger Wires (Used to trigger the relays when battery power is keyed on. You will need to tap into your factory FPDM wire to trigger the relays. See chart below.)

 

The small Black wires with the ring terminal on them are your ground. You will ground the ring terminal to a good ground on the chassis. If there is paint or any type of coating on the place where you intend to ground the relays you will need to use some sandpaper to remove the paint/coating in order to get a proper ground

Fuses:

Each relay has a blade fuse between the relay itself and the pump. If there is a short at the pump the fuse will pop protecting the relay and anything in line before the relay from shorting out.

The 6-Pin Connector and Wire Colors

The 6-pin connector at the end of the triple relay harness was designed to work as a plug and play solution for the 2005+ Mustang fuel hats. The connector at the end of the wire harness will mate directly to the 6 pin pigtail harness for power and ground to all 3 pumps. The pigtail installs onto the power and ground wires coming out of the fuel hat; red to red for power wires and black to black for Ground. You'll be left with 2 remaining wires on the fuel hat which are for the level sender. You will need to peel back the wire loom from your factory harness where it used to connect to the factory fuel hat assembly. Depending on the model/year you will see several larger gauge wires which are for the fuel pump power and ground. There will also be 2 smaller gauge wires which are for the level sender. We typically connect the yellow wire on the Lethal harness to the small colored wire on the factory harness and the black wire to the dark color. However on 2005+ cars it's not imperative to match colors for the levels senders as the sending units run off of resistance not power and ground. So you can connect the level sender wires any way you like and they will allow the sending unit to function properly.

 

Which wire do I tap into to trigger the relays for my return style fuel system?

99-04 GT/Mach-1/99-01 Cobra – Pink/Black FPDM Wire

2003-2004 Cobra – Yellow/Green FPDM Wire

2005-2009 Mustang GT / GT500 White FPDM Wire

2010-2014 GT / GT500 – Violet With Green Tracer FPDM Wire

2011+ Mustang GT – Yellow with Grey Tracer FPDM Wire

 

 

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Fuel Hats for your 1999-up Mustang

 

Which hat and why?

The 1999-2004 Mustang GT/ Mach 1/Cobra use the DX-SN016 dual pump hat (for 2 pumps)or the DX-SN019 triple pump fuel hat (for 3 pumps).

If you have a 2005-2010 Mustang GT or a 2007-2012 Shelby GT500, you'll want to use the DX-0700-2 fuel hat.

If you have a 2011-up Mustang GT, Boss 302, GT350 or EcoBoost you will want to use the DX-0711 hat. You can use that same DX-0711 fuel hat in the 2013-14 Shelby GT500 and the new 2020+ Shelby GT500.

DX-SN016: Dual Pump Hat for your 1999-2004 Mustang GT/Mach 1/Cobra

The DX-SN016 is a dual pump fuel hat designed to work in the factory 03-04 Cobra fuel tank and use the 03-04 Cobra factory level sender. It's a direct replacement for the factory fuel pump assembly when switching to a return style setup.

 

This hat will also work in all 99-04 GT's, the 03-04 Mach 1 and the 99-01 Cobra. However, since the fuel tank in these vehicles use a different fuel tank assembly it's required to remove the plastic piece at the bottom of the the tank in order for the DX-SN016 fuel hat to fit. This can be easily accomplished in a very short amount of time with simple hand tools. Keep in mind that the GT, Mach 1 and 99-01 Cobra tanks do not have a baffle system like the 03-04 Cobra does so we recommend running at least ½ full tank of fuel when driving the car hard or racing it. This is to prevent fuel starvation to the pumps from sloshing.

NOTE: Since the 99-04 GT, 03-04 Mach 1 and 99-01 Cobra also use a different level sender the options are to purchase the DX-37011 level sender bracket which allows you to use your factory GT/Mach-1 and 99-01 Cobra level sender and mate it to the DX-SN016 fuel hat OR the other option would be to purchase an OEM 03-04 Cobra level sender from us which bolts directly to the spine of our fuel hat.

Connecting the level sender

The level sender has 1 yellow wire coming off it it. That will be connected to the yellow wire on the underside of the fuel hat using the supplied spade connector. You'll then ground the black wire with the ring terminal onto the spine as pictured in the image below.

DX-SN019: Triple Pump Hat for your 1999-2004 Mustang GT/Mach 1/Cobra

The DX-SN019 is a triple pump fuel hat designed to work in the factory 03-04 Cobra fuel tank as well as use the 03-04 factory level sender.The DX-SN019 is a direct replacement for the factory fuel pump assembly for a 03-04 Cobra when switching to a return style fuel system. This hat will also work in all 99-04 GT's, 03-04 Mach 1 and 99-01 Cobras. However since the fuel tank in these vehicles use a different fuel tank assembly it's required to remove the plastic piece at the bottom of the the tank in order for the DX-SN019 fuel hat to fit. This can be easily accomplished in a very short amount of time with simple hand tools. Keep in mind that the GT, Mach 1 and 99-01 Cobra tanks do not have a baffle system like the 03-04 Cobra does so we recommend running at least ½ full tank of fuel when driving the car hard or racing it. This is to prevent fuel starvation to the pumps from sloshing.

Wiring the DX-SN019

The DX-SN019 triple pump fuel hat can be setup as plug and play with our triple pump fuel harness and triple pump wiring pigtail. The wires on the pigtail will connect with butt connectors and heat shrink to the wires on the fuel hat. Red wires are positive (+) and the Black Wires on the pigtail are negative (-). Once the pigtail is installed the connector at the end of the triple pump wiring harness will plug directly into the pigtail which was wired onto the fuel hat.

Connecting the level sender

The level sender has 1 yellow wire coming off it it. That will be connected to the yellow wire on the underside of the fuel hat using the supplied spade connector. You will then ground the black wire with the ring terminal onto the spine as pictured below.

 

DX-0700-2: Triple Pump Hat for your 2005-2010 Mustang GT and 2007-2012 Shelby GT500

The DivisionX DX-0700-2 is the answer to all of your fueling needs. It's machined from high quality billet aluminum right here in the USA and anodized black for a long lasting protective finish.

All of the wiring on the fuel hat is plug and play with the fuel pump connectors on the underside of the fuel hat and the 6 pin OEM connector on the top of the hat to make installation much easier. The red wires are for power and the black wires are ground. The additional 2 smaller gauge wires (yellow) are for the fuel level sending unit. The wiring on the DivisionX fuel hat is sealed with a propriety plug design that prevents fuel from leaking out of the tank through the wiring. The DivisionX hat also installs into the factory fuel tank using the OEM o-ring and metal ring to secure it in place.

The hat comes with a 10an feed port and 8an return port which accept o-ring boss fittings. So if you wanted to do an 8an feed and 6an return instead a simple swap of fittings and you have it set up exactly how you want it.

Fuel level sender

Since this is a drop in replacement for your factory fuel pump assembly it’s going to register fuel levels on your dash just like it does from the factory. All you'll do is swap your factory fuel level sender over to the DivisionX hat and you'll read fuel levels just like you did before.

DX-0711: Triple Pump Hat for your 2011-up Mustang GT, EcoBoost, Boss 302 and GT350 as well as the 2013-14 and 2020 Shelby GT500

The DivisionX DX-0711 is the answer to all of your fueling needs. It's machined from high quality billet aluminum right here in the USA and anodized black for a long lasting protective finish. The DivisionX S197-C fuel hat manifold is designed to run up to three fuel pumps.

 

All of the wiring on the fuel hat is plug and play with the fuel pump connectors on the underside of the fuel hat and the 6 pin OEM connector on the top of the hat to make installation much easier. The red wires are for power and the black wires are ground. The additional 2 smaller gauge wires (yellow) are for the fuel level sending unit. The wiring on the DivisionX fuel hat is sealed with a propriety plug design that prevents fuel from leaking out of the tank through the wiring. The DivisionX hat also installs into the factory fuel tank using the OEM o-ring and metal ring to secure it in place.

The hat comes with a 10an feed port and 8an return port which accept o-ring boss fittings. So if you wanted to do an 8an feed and 6an return instead a simple swap of fittings and you have it set up exactly how you want it.

Fuel level sender

Since this is a drop in replacement for your factory fuel pump assembly it’s going to register fuel levels on your dash just like it does from the factory. All you'll do is swap your factory fuel level sender over to the DivisionX hat and you'll read fuel levels just like you did before.

2005-up Mustang: The Venturi

All 2005+ mustangs use a saddle style fuel tank. That means there's two sides to the tank. The drivers side and passenger side. There's a hose that goes from the passenger side to the rivers side that attaches to the pump assembly which continually pulls fuel from the passenger side until it's empty. It does this by using a venturi effect. This process works identical with the DivisionX fuel hat as it does on the factory pump assembly.

Fuel Pump Compatibility

The above mentioned fuel hats both accept a wide variety of fuel pumps. The pumps listed below are confirmed to fit in these fuel hats

  • Walbro GSS342
  • Aeromotive 340lph
  • AEM 340lph
  • DivisionX 340S
  • Walbro F900000262
  • Walbro F900000267
  • Walbro F900000274
  • Walbro F900000285 (trimming of the pump nipple is required)
  • Walbro F900000295 (trimming of the pump nipple is required)
 

NOTE: If you are using the Walbro GSS342 fuel pumps you will need to make sure and order the fuel hat with the correct pigtail on the underside of the hat for it to be plug and play. Otherwise most of (if not all of) the other pumps use the Delphi connector that the F90000- series pumps use.

Fuel Pump Flow Chart

Here are the flow numbers at multiple psi for your reference.

 

Fuel Pump Bottoming Out?

We have seen over the years that even though the correct measurement is done for the pumps in the fuel hat (see image below for reference) that it still bottoms out on the bottom of the fuel tank causing the pre-filters to get crushed and starve the pumps for fuel. This is very common as the tank bottom is made of a material that's easily bent. If the vehicle has been serviced before it's possible a floor jack or other device was used to secure or lift the tank which could potentially bend the tank bottom up creating a clearance issue for the pumps. You will be able to notice this when installing the fuel hat into the tank. If the hat doesn't sit flush onto the gasket it's most likely due to the measurement of the pumps not being done correctly or the tank is bent. If the tank is bent it can be easily fixed with a piece of wood and a rubber mallet. You'll gently hit the piece of wood with the mallet from the opening in the tank downward. This should pop the tank bottom back into place allowing the fuel hat to sit flush and have proper pump height clearance.

Running 2 pumps in a triple pump fuel hat

What if I only want to run two pumps in a triple pump fuel hat?

Not a problem, you can easily do this. We actually recommend only installing the pumps that will be used. That means if you only want to run two pumps only install 2 pumps. If you want to run 3 pumps then install the 3 pumps. If only 2 pumps are installed on a triple pump fuel hat you will need to make sure that the inlet on the underside of the fuel hat for the 3rd pump is plugged with the supplied o-ring port plug. This way fuel from your other two pumps doesn't bleed pressure and fuel back into the tank through that third pump inlet.

What if I have a triple pump harness and only want to run 2 pumps?

Again, not a problem!You can install the triple pump harness the same way as you would if you were going to run all 3 pumps. However you'll remove the relay and fuse from the harness for that third pump.

Can I run 2 pumps now and 3 pumps later?

Yes. The fuel hat as mentioned is designed to accept up to 3 pumps. You can run 2 pumps and add a 3rd pump later on with the supplied hardware to either block off the 3rd pump feed or connect it to the pump.

Can I run 3 pumps in the hat but have 2 run full time and the 3rd kick on later?

Yep! All you need is our Hobbs Pressure Switch setup which you can use to trigger the 3rd pump once it see's 5psi of boost pressure. The 3rd pump will still be wired in and functional but only work once the 5psi is achieved.

 

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Fuel System Installation

 

Each Lethal Performance fuel system has multiple components to it. Each main component will have it's own installation instructions which are available for download on the product page of the fuel system you purchased. You will want to follow the specific instructions for each component of the system to achieve the proper installation. We also provide fuel system hose routing diagrams on the same product page. These are very helpful to show you which fitting goes where, where the regulator mounts and how the fuel hoses are run between the fuel hat, rails, etc.

Do I need to use any type of silicone or sealant on my fuel fittings or hose ends?

Most of the fittings we use in our systems are flare fittings which seal by themselves when tightened and do not require any type of sealant. This includes fuel filter fittings, fuel rail end fittings, fuel hat fittings and any other fitting that our fuel hoses connect to. The only fittings in our systems which are NPT threaded are there the fuel pressure gauge mounts to the regulator as well as the 1/8” NPT ports on the fuel rails. When installing the fuel pressure gauge to the port on the fuel pressure regulator or onto the fuel rail we recommend using teflon paste. You'll want to do this without any pressure in the lines as well as making sure everything is clean and free of debris. Simply put the teflon paste on the threaded portion of the gauge and install it into the port making sure to secure it well without over tightening it. If you are not using the 1/8” NPT ports on the fuel rails you'll plug them with the 1/8” NPT port plugs using the same technique and teflon paste. Do not overnighten these as you can strip the hex pattern on the plug and it will then need to be removed by a machine shop.

>What about a Hobbs Switch?

Do you need to run a Hobbs switch to turn on an additional pump or two? Our experience is no. We have been running our dual and triple pump setups for a very long time in both street and strip applications. At no point have we ever experienced any type of issues while running 2 or 3 pumps full time. With that said if you are worried about this we do offer a 5psi Hobbs switch setup. How to wire the Hobbs Switch

If you decide to run a Hobbs switch there are 2 wires involved as well as a vacuum/boost line. You will connect the Hobbs switch to a boost/vac source with the provided T-fitting and vacuum hose. You will then wire the switch into the BLUE trigger wires on the relaysetup on either our dual or triple pump wiring harness. You will simply cut the blue trigger wire and connect 1 wire from the hobbs switch to the blue wire going into the relay and the other wire will go wire side to the wire that's going away from the relay to the key on power source. This way once the achieved boost is met on the hobbs switch it will close the loop and allow power to go to the pump or pumps you would like to be on the Hobbs switch.

 

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Fuel Hose

 

 

All of our systems come standard with the Fragola PTFE fuel hose with the option to replace it with the Fragola Pushlite hose. Read below to find out which fuel hose is best for you.

Fragola PTFE Fuel Hose

This hose is very high quality and will not have any type of smell from fuel weep when using alternative types of fuel such as E85 or equivalent. The PTFE hose from Fragola has an inner PTFE/teflon lining which is then covered in a stainless steel woven braid. We then cover the stainless braid with a black protective vinyl sleeve which looks great and protects the engine bay and chassis from being scuffed by the stainless braided line inside of it. The PTFE hose is easy to work with however you do want to make sure you do not kink it during install as that can compromise the structural integrity of the hose and may require being replaced. It's ok if the black vinyl coating is scraped off to the stainless braid. This will not affect anything negatively as the black coating is just an added layer of protection to look cleaner and protect the engine bay/chassis from being scratched or scuffed.

Pictured: Our pre-assembled PTFE hose kits give a super clean finishing look to your fuel system.

Fragola Pushlite Fuel Hose

We have had great success with this hose over many years on our cars as well as our customers cars. It is less expensive than the PTFE hose and is also very easy to work with. However, we have found that the standard pushlite hose is permeable so if you are running E85 or let the car sit for long periods of time you will experience fuel smell from it.

 

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Setting Up Your Fuel Pressure Regulator

The Regulators

Each regulator we include in our fuel systems are boost reference regulators. We use regulators from both Magnafuel (found mostly in our 1999-2004 Mustang budget fuel systems) and Aeromotive. These regulators are made specifically for divisionX to be used in your own setups as well as in our return style fuel systems.

Regulator Links:

Boost reference? What does that mean?

It means that fuel pressure raises and lowers as the regulator sees boost/vacuum. In most cases the side ports of the regulators are for the feeds and the bottom port is the return. Once the fuel system is installed and has been checked for leaks you can set the pressure on the regulator. The base fuel pressure setting is usually recommended by your tuner so make sure to ask them what they would like the base pressure set at before doing anything.

For this example we'll use 40psi as a base pressure. With the boost/vacuum line removed from the port on the regulator you'll key the car on so that the pumps are running full time. Check the pressure gauge at the regulator or fuel rail. You will then loosen the nut at the top of the regulator with a wrench and allen key. Gently rotate the screw with the allen key. Clockwise is to increase pressure, counter clockwise is to lower fuel pressure. Once the desired pressure is achieved hold the allen key in place and tighten the nut to lock the screw in place. Once that's done double check and make sure that the fuel pressure is locked in where you want it.

 

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Deadhead Vs. Traditional Fuel Systems

 

There are two ways to route the return style fuel system: deadhead and traditional style.

Deadhead Fuel System

This is where the fuel pressure regulator is placed before the fuel rails and the fuel lines from the regulator feed the rails. The other ends of the rails are plugged creating a deadhead and fuel doesn't get returned from the rails to the regulator.

Traditional Fuel System

This is where the fuel pressure regulator is placed after the fuel rails. Fuel is fed to the fuel rails from the main feed line (usually through aY-block) then exits the other end of the rails where it's then fed to the regulator and then returned to the tank.

 

Both of these systems work very well. We have used both setups on several project cars of ours over the years as well as have hundreds and hundreds of customers running their systems the same way. If you are unsure of which setup to run it's best to consult your tuner as they may prefer one setup over another.

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